osgdem is utility program for reading geospatial imagery and digital elevation maps (DEM's) and generating large scale 3D terrain databases that OpenSceneGraph applications can load and browse in real-time. What follows is a step-by-step guide to using osgdem, followed by a list of full options available.

Quick step by step guide

What follows are the steps required to get osgTerrain/osgdem compiling and an example of how to use it to process imagery and DEM's to generate a paged databases.

7. Now its time to run the osgdem example to generate your PagedLOD database, the more levels you generate the longer it will take (exponentially so). 'osgdem' is just a front end to osgTerrain::DataSet where all the hard work happens. Here's what to run :

Then go away for lunch, afternoon and tea, as generating this much data takes a while... If you don't wish to wait for the full database then reduce the number of levels it generates by setting the -l option to a lower value such as 3.
The command line options used above are:
The first part the --xx and --yy is specifying the size of the pixels in meters, since these png/tif don't have any geospatial data of their own, if you have geospatialised files then you won't need this.

The second part -t <filename> is the option for specificing the texture maps to use, you can use as many times as you wish, osgTerrain::DataSet will moziac them into a single database.

The third part -d is the option for specifying the digital elevation maps to use, as with the textures you can use as many as you like.

The -l option specificies the maximum number of levels to generate. If you use a large number then the database generation will stop once the max resolution of your source data is matched by the resulting database. The database generation will decend further where there is high res source data, decend less where there is lower res data.

The -v option specifies the scaling factor which the height is multiplied by.

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The -o <filename> is the output format to generate the databases in. This will be the name of the topmost file in the one you should load. It can be a .ive or a .osg. The .ive is faster and has embedded files.

And finally the -a <filename> tells the osgdem to write all tiles to a single archive, in this a the OpenSceneGraph native archive format, which uses the extension .osga to disguinish itself. The use of archives is not required, but is recommend since it makes managment of the whole database much more convinient - you have a single file to manage rather than what could be 10's of thousands as is the case of large databases.

8. Time to play. Simply load the database in your app, and if you've based it on osgViewer::Viewer or CompositeViewer all the paging support is already built in. The standard osgviewer works just fine so, here goes:

osgviewer pegout.osga

9. If your imagery and DEMs have geospatial coords associated with them then the -xx, --yy and -v options will not be required, making it much simplier to specify - you just need to specifiy options such as -t imge.tif and -d terran.dt0 without any need to set the coordinate system.

10. osgdem can automatically handle mosaicing of sets of files. These can be specified via a sequence of -t <filename> and -d <filename> pairs on the commandline, or via -t <directoryname> and -d <directoryname>.

Commandline options

Parameter

Description

Default

General

-h or --help

Display commandline arguments information

--task

-s

--so

--report

--cache <filename>

Read the cache file to use a look up for locally cached files.

--version

Print out version

--version-number

Print out version number only.

--comment

Added a comment/description string to the top most node in the dataset

empty

--split

Set the distributed build split level.

--splits

Set the distributed build primary and secondary split levels.

--run-path

Set the path that the build should be run from.

--notify-level

Set the notify level when logging messages.

Input

-d <filename>

Specify the digital elevation map input file to process

-t <filename>

Specify the texture map input file to process

--building <filename>

Specify building outlines using shapefiles.

--forest <filename>

Specify forest outlines using shapefiles

--levels <begin_level> <end_level>

Specify the range of levels that the next source Texture or DEM will contribute to.

--layer <layer_num>

Specify the layer that the next source Texture will contribute to..

Coordinate system

--cs <coordinates system string>

Set the coordinates system of source imagery, DEM or destination database. The string may be any of the usual GDAL/OGR forms, complete WKT, PROJ.4, EPS

--wkt <WKT string>

Set the coordinates system of source imagery, DEM or destination database in WellKownText form.

--wkt-file <WKT file>

Set the coordinates system of source imagery, DEM or destination database by as file containing WellKownText definition.

Geocentric database

--geocentric

Build a database in geocentric (i.e. whole earth) database.

--bluemarble-east

Set the coordinates system for next texture or dem to represent the eastern hemisphere of the earth.

--bluemarble-west

Set the coordinates system for next texture or dem to represent the western hemisphere of the earth.

--whole-globe

Set the coordinates system for next texture or dem to represent the whole hemisphere of the earth.

--radius-polar

Set the polar radius of the ellipsoid model when building a geocentric database.

6356752.3142

--radius-equator

Set the equatorial radius of the ellipsoid model when building a geocentric database.

6378137

--spherical

Set the polar and equatorial radius both to the average of the two.

Flat database

--range <xMin> <xMax> <yMin> <yMax>

Set the coordinates system for next texture or dem to the given range.

Use mip mapped textures, and generate the mipmaps in hardware when available.

--mip-mapping-imagery

Use mip mapped textures, and generate the mipmaps in imagery. (default)

--BuildOverlays [True/False]

Switch on/off the building of overlay within the source imagery. Overlays can help reduce texture aliasing artifacts.

--ReprojectSources [True/False]

Switch on/off the reprojection of any source imagery that aren't in the correct projection for the database build.

--GenerateTiles [True/False]

Switch on/off the generation of the output database tiles.

--tile-image-size

Set the tile maximum image size

256

--tile-terrain-size

Set the tile maximum terrain size

64

-O

string option to pass to write plugins, use "" for multiple options

--subtile <LOD> <X> <Y>

Set the subtile to begin the build from.

--record-subtile-on-leaf-tiles

Enable the setting of the subtile file name of the leaf tiles.

--type-attribute

Set the type name which specify how the shapes should be interpreted in shapefile/dbase files. (empty signifies no type attribute has been defined)

empty

--height-attribute

Set the attribute name for height attributes used in shapefile/dbase files.

--height

Set the height to use for associated shapefiles. (negative signifies that no height has been defined)

-1.0

--mask

Set the mask to assign indivual shapefile/model.

0xffffffff

--terrain-mask

Set the overall mask to assign terrain.

0xffffffff

--read-threads-ratio <ratio>

Set the ratio number of read threads relative to number of cores to use.

0.0

--write-threads-ratio <ratio>

Set the ratio number of write threads relative to number of cores to use.

0.0

--build-options <string>

Set build options string.

DEM interpolation

--interpolate-terrain

Enable the use of interpolation when sampling data from source DEMs. (default)

--no-interpolate-terrain

Disable the use of interpolation when sampling data from source DEMs.

Imagery interpolation

--interpolate-imagery

Enable the use of interpolation when sampling data from source imagery. (default)

--no-interpolate-imagery

Disable the use of interpolation when sampling data from source imagery.

Coordinate System Tips

WKT coordinate system definition format is a very comprehensive, but difficult to use as a "human enter-able" specifier for coordinate systems. osgdem uses GDAL under the hood which also allows definition of the --cs flag in PROJ4 format. PROJ4's definition format is much more human friendly.
Examples: